1. Field of the Invention
The present invention relates to a liquid discharge head and a manufacturing method thereof, and more particularly to a technique of using a deposition method in the manufacture of a liquid discharge head.
2. Description of the Related Art
Recently, in the field of the micro electrical mechanical systems (MEMS), it is considered that the devices using piezoelectric ceramics, such as sensors and actuators, have reached a higher level of integration and these elements are fabricated by a film formation that is suitable for practical use. As a case in point, an aerosol deposition method is known as a deposition technique for ceramics, a metal, or the like. In the aerosol deposition method, aerosol is made from powder of raw material, the aerosol is sprayed onto a substrate, and a film is formed on the substrate by deposition of the powdered material due to its impact energy.
When an inkjet head or another such liquid discharge head is manufactured, the main target product formed by the aerosol deposition method is a piezoelectric member for driving a diaphragm. Japanese Patent Application Publication No. 2003-136714 suggests a method for manufacturing a liquid discharge head wherein a diaphragm made from a metal oxide material is formed on a substrate made from a corrosion-resistant metal material according to the aerosol deposition method. In the manufacturing, after the diaphragm is formed on the substrate according to the aerosol deposition method, the portions of the substrate that server as ink liquid chambers (pressure chambers) are removed by etching, so that the substrate forms pressure chamber dividing walls.
In general, the diaphragms and the pressure chamber dividing walls in the inkjet head are affixed together by adhesive. On the other hand, the method suggested in Japanese Patent Application Publication No. 2003-136714 has merits that there is no need for an adhesion step for affixing the diaphragms with the pressure chamber dividing walls, because the diaphragms are formed according to the aerosol deposition method on the substrate that serves as the pressure chamber dividing walls.
However, the manufacturing method suggested in Japanese Patent Application Publication No. 2003-136714 is problematic in that it comprises a step for etching the substrate in order to form pressure chambers facing the diaphragms after the diaphragms are formed according to the aerosol deposition method, and hence the number of processes increases. There is no conventional technique in which the pressure chamber dividing walls are formed according to the aerosol deposition method.
Furthermore, the base part of the inkjet head has a three-dimensional structure defining spaces such as pressure chambers, which are filled with ink, and common flow paths for supplying ink to the pressure chambers. Miniaturization of this three-dimensional structure is essential if the nozzle density is to be increased in order to achieve high-quality of images formed by the inkjet head.
In the method of manufacture according to Japanese Patent Application Publication No. 2003-136714, pressure chambers are formed by etching a substrate; however, it is difficult to form complex spaces including the aforementioned flow paths, and the like, in the substrate, in addition to the pressure chambers, by etching the same substrate. The base part of the inkjet head generally has a multiple-layer substrate structure in which a plurality of substrates are bonded together in order to achieve a three-dimensional structure. Therefore, it is difficult to achieve downsizing, such as formation of a thin-film structure, formation of a fine structure, or the like. Moreover, if a three-dimensional structure is formed by means of a multiple-layer substrate, it is difficult to obtain a fine structure, due to problems of machining accuracy, breakages, warping and other stress damage. Further, in a structure which is formed with bonding by means of an adhesive, there has been a problem of uneven discharge pressure in the head, due to variations in the bonding layer or variations in the bonding strength. Furthermore, since the adhesive itself is an organic material, there have been problems in that the bonding force is liable to change over time, as well as stress-related change in properties over time, and hence improvements in durability are sought.